Were you using landline integration? Meaning you chose to use your own number with Ooma (your own number used to be a landline and you fed the landline dialtone to your Ooma's "wall" port before you cancelled your landline)?

If this is the case, after you cancelled your landline, did you call into Ooma customer service to change your Ooma setup from landline integration to standalone mode?

If haven't done so yet, you'd want to do that first. They will change your setup and ask you to reboot your Ooma.